This invention relates to techniques for the non-destructive testing of structures, and, in particular, to economical and time-conserving techniques for moving one or more non-destructive sensors relative to the portion of the structure to be tested.
Non-destructive testing of structures involves thoroughly examining a structure without harming the structure or requiring significant disassembly of the structure. Non-destructive testing is advantageous for many applications in which a thorough inspection of the exterior and/or interior of a structure is required. For example, non-destructive testing is commonly utilized in the aircraft industry to inspect aircraft structures for any type of internal or external damage to the structure. Metallic aircraft structures are typically inspected for corrosion and/or cracking, particularly near fasteners in the structure. Composite structures are typically inspected for any type of damage occurring anywhere on or within the composite material.
Various types of sensors may be utilized to perform non-destructive testing. One or more sensors may move over the portion of the structure to be examined, and receive data regarding the structure. For example, a pulse-echo, thru-transmission, or shear wave sensor may be utilized to obtain ultrasonic data, such as thickness gauging, detection of laminar defects and porosity, and/or crack detection in the structure. Resonance, pitch/catch or mechanical impedance sensors may be utilized to provide indications of voids or porosity, such as in adhesive bondlines of the structure. In addition, single and dual current eddy current sensors impart and detect eddy currents within a structure so as to identify cracks and/or corrosion, particularly in metallic or other conductive structures. The data acquired by the sensors is typically processed by a processing element, and the processed data may be presented to a user via a display.
In many cases, structures must be inspected in the field because it is either not feasible or too expensive and time-consuming to transport the structure to an off-site laboratory for the inspection. For routine field inspections of structures, technicians typically manually scan the structures with an appropriate sensor. The manual scanning generally consists of a trained technician holding a sensor and moving the sensor along the structure to ensure the sensor is capable of testing all desired portions of the structure. In many situations, the technician must repeatedly move the sensor side-to-side in one direction while simultaneously indexing the sensor approximately one-fourth of an inch in another direction. For a technician standing beside a structure, the technician may repeatedly move the sensor right and left, and back again, while indexing the sensor about one-fourth of an inch between each pass. In addition, because the sensors typically do not associate location information with the acquired data, the same technician who is manually scanning the structure must also watch the sensor display while scanning the structure to determine where the defects, if any, are located in the structure. The quality of the inspection, therefore, depends in large part upon the technician""s performance, not only regarding the motion of the sensor, but also the attentiveness of the technician and interpreting the displayed data. Thus, manual scanning of structures, is time-consuming, labor-intensive, and prone to human error. Furthermore, manual scanning may cause fatigue and/or other health problems for technicians, such as Repetitive Motion Disorders.
Automated inspection systems have been developed, but the automated systems may sometimes be too expensive and/or bulky to be utilized for routine field inspections. For example, the Mobile Automated Scanner (M.A.U.S.), developed by The Boeing Company, provides automated data acquisition in a portable package for on-site inspections. One type of M.A.U.S. system automatically moves along the structure via strategically controlled suction cups, while another type includes handheld sensors and an associated carriage that is moved along the structure via manual motion. As such, the M.A.U.S. system not only scans the structure, but also processes the data regarding the structure, and associates the data with the exact location on the structure from where the data was obtained. While the M.A.U.S. system is portable, provides fast inspection rates, and employs any type of sensor, such as those mentioned above, it may also be large and somewhat expensive due to the processing element(s) required to provide the detailed data regarding the scanned portion of the structure. In addition, the M.A.U.S. system is not capable of being powered by a local power supply, such as batteries, and therefore requires a connection to a remote power supply via bulky power cable(s), which hinders the ease of use of the system. Additionally, the version of the M.A.U.S. system that includes handheld sensors is similarly limited by the relatively large size of the handheld sensors and the associated cabling. As such, it may not be feasible to utilize the M.A.U.S. system for routine field inspections.
Therefore, a need exists for a portable scanning technique that reduces the tasks technicians must perform as compared to a manual scanning technique. The need is also for a technique that is lower cost and easier to use than conventional automated scanning techniques.
The apparatus and method for moving a sensor in at least one direction according to the present invention provides a technique for scanning a workpiece with a scanner that is more compact and lower in cost than the conventional automated scanning techniques. Furthermore, the scanning technique provided by the present invention is partially automated, such that the amount of physical labor performed by a scanning technician is greatly reduced. Thus, the present invention provides a low cost and time-saving scanning technique that may be efficiently utilized for many applications, even routine field inspections of various structures.
The apparatus for providing a combination of automated and manual movement of a non-destructive test (NDT) sensor according to the present invention includes an NDT sensor, a housing and an actuating member. The NDT sensor is carried by the actuating member, and the actuating member is at least partially disposed within the housing. The actuating member is adapted for automated movement in one direction, while the housing is configured to be grasped by an operator and manually moved in another direction. The sensor may be secured to the actuating member with at least one adjustment member. One example of a sensor that may be used is an eddy current sensor.
According to the method for providing a combination of automated and manual movement of an NDT sensor, once the sensor is positioned proximate a workpiece, the sensor may be automatically moved in one direction with respect to the workpiece without manual intervention, and manually moved in another direction, such that the sensor is moved by the combination of automated and manual movement. For instance the manual motion may be in a direction at least substantially normal to the automatic movement.
The actuating member may have at least two substantially parallel arms extending from near the sensor, which permits the sensor to contact the surface while maintaining the sensor in a substantially normal relationship to the surface of the workpiece. In one embodiment of an apparatus for moving a sensor over a workpiece, the apparatus includes a sensor and the actuating member having the parallel arms described above. Thus, the sensor attached to the actuating member may be positioned proximate the workpiece, and the sensor may then slide along the surface such that the sensor continuously contacts the surface and is maintained in a substantially normal relationship to the surface of the workpiece while it slides.
The apparatus also may include a cam having an eccentric collar. As the cam rotates, the eccentric collar may slide within an elongated opening defined by the actuating member, which, in turn, causes the sensor to move in the one direction. The elongated opening is located a distance from the sensor, and a motor may be used to cause the cam to rotate.
Embodiments of the present invention may also involve attaching a pivot piece to the actuating member a predetermined distance from the sensor. The actuating member is then capable of at least partially pivoting about the pivot piece to cause the sensor to move in the one direction. In further embodiments of the present invention, the actuating member may be balanced, such as by attaching a weight to the actuating member opposite the sensor relative to the pivot piece. In embodiments of the present invention in which the actuating member has at least two substantially parallel arms, the arms may extend from the sensor to the pivot piece.
Thus, the apparatus and method for moving a sensor in at least one direction along a surface provides a low cost, and efficient technique for scanning the surface of a structure with a non-destructive sensor. In particular, the scanning technique of the present invention is less expensive, more compact, and easier to use than conventional automated scanning techniques, while also less time-consuming, more exact, and takes less of a physical toll on a scanning technician than conventional manual scanning techniques.